Global solar spectrum devices and methods

ABSTRACT

Solar spectral irradiance (SSI) measurements are important for solar collector/photovoltaic panel efficiency and solar energy resource assessment as well as being important for scientific meteorological/climate observations and material testing research. To date such measurements have exploited modified diffraction grating based scientific instruments which are bulky, expensive, and with low mechanical integrity for generalized deployment. A compact and cost-effective tool for accurately determining the global solar spectra as well as the global horizontal or tilted irradiances as part of on-site solar resource assessments and module performance characterization studies would be beneficial. An instrument with no moving parts for mechanical and environment stability in open field, non-controlled deployments could exploit software to resolve the global, direct and diffuse solar spectra from its measurements within the 280-4000 nm spectral range, in addition to major atmospheric processes, such as air mass, Rayleigh scattering, aerosol extinction, ozone and water vapor absorptions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This specification claims the benefit of priority as 371 National PhaseEntry application of PCT/CA2016/000,264 entitled “Global Solar SpectrumDevices and Methods” filed Oct. 20, 2016, which itself claims thebenefit of priority from U.S. Provisional Patent Application 62/243,706filed Oct. 20, 2015 entitled “Global Solar Spectrum Devices andMethods”, the entire contents of each being incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to global solar spectral irradiance and moreparticularly to compact, no-moving part field deployable devices andmethods of measuring and resolving global, direct and diffuse solarspectral irradiance, direct normal irradiance together with aerosol,water vapour and ozone spectral absorption profiles.

BACKGROUND OF THE INVENTION

Solar energy is the radiant light and heat from the Sun harnessed usinga range of ever-evolving technologies such as solar heating,photovoltaics, solar thermal energy, solar architecture and artificialphotosynthesis. It is an important source of renewable energy and itstechnologies are broadly characterized as either passive solar or activesolar depending on the way they capture and distribute solar energy orconvert it into solar power. Active solar techniques include the use ofphotovoltaic systems, concentrated solar power and solar water heatingto harness the energy. Passive solar techniques include orienting abuilding to the Sun, selecting materials with favorable thermal mass orlight dispersing properties, and designing spaces that naturallycirculate air.

Photovoltaic cells, commonly referred to as solar cells, are electricaldevices that convert incident light within their wavelength range ofoperation into electricity for immediate use or subsequent use throughstorage within a battery. Historically, two time-of-day dependentfactors have complicated both the characterization of photovoltaicmodule and array performance and projected power generation in differentdeployment locations. These factors are the changes in the solarspectrum over the day and optical effects arising from solarangle-of-incidence. Accordingly, solar spectral irradiance (SSI)measurements are important for solar collector/photovoltaic panelefficiency and solar energy resource assessment. However, they are alsoimportant for scientific meteorological/climate observations andmaterial testing research.

To date SSI measurements exploit modified scientific instruments basedupon diffraction gratings and accordingly are generally defined by beingbulky, expensive, and with low mechanical integrity for generalizeddeployment. Accordingly, it would be beneficial to provide a compact andcost-effective tool for accurately determining the global solar spectraas well as the global horizontal or tilted irradiances as part ofon-site solar resource assessments and module performancecharacterization studies. It would be further beneficial for the tool tohave no moving parts for mechanical and environment stability in openfield, non-controlled deployments and to exploit software to resolve theglobal, direct and diffuse solar spectra from its measurements withinthe 280-4000 nm spectral range, in addition to major atmosphericprocesses, such as air mass, Rayleigh scattering, aerosol extinction,ozone and water vapour absorptions.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

SUMMARY OF THE INVENTION

It is an object of the present invention to mitigate limitations withinthe prior art relating to global solar spectral irradiance and moreparticularly to compact, no-moving part field deployable devices andmethods of measuring and resolving global, direct and diffuse solarspectral irradiance, together with aerosol, water vapour and ozonespectral absorption profiles.

In accordance with an embodiment of the invention there is provided adevice comprising

-   a spherical diffuser comprising a spherical cavity within an outer    body, the spherical cavity coated with a first near Lambertian    material;-   a first aperture of a first predetermined diameter formed in a first    predetermined position on the spherical diffuser;-   a second aperture of a second predetermined diameter formed in a    second predetermined position on the spherical diffuser;-   a baffle disposed in a predetermined relationship relative to the    first aperture and the second aperture, the baffle having a    predetermined thickness, is coated with a second near Lambertian    material and is disposed on the inner surface of the spherical    diffuser and having a geometry defining a predetermined portion of a    sphere;-   a plurality of optical collimators coupled to the second aperture    and defining a maximum angular acceptance angle for each    photodetector of a plurality of photodetectors disposed at the    distal end of an optical collimator from that coupled to the second    aperture; and-   a plurality of optical filters, each filter having a passband of    predetermined optical wavelengths and disposed in combination with    an optical collimator of the plurality of collimators to filter    optical signals exiting the second aperture.

In accordance with an embodiment of the invention there is provided adevice comprising

-   a plurality of first photodetectors, each first photodetector    receiving a predetermined wavelength range of the ambient optical    environment via an optical path comprising a diffuser element, a    bandpass filter, and an optical collimator to limit the angle of    incident ambient light within a predetermined field of view;-   a plurality of second photodetectors arranged radially around a post    projecting above the upper surface of the plurality of second    photodetectors; and-   an electronic circuit comprising a first portion for digitizing a    photocurrent for each first photodetector of the plurality of first    photodetectors, a second portion for digitizing a photocurrent for    each second photodetector of the plurality of second photodetectors,    and a third portion for generating a reconstructed solar spectrum in    dependence upon at least the digitized photocurrents of the    plurality of first photodetectors, the digitized photocurrents of    the plurality of second photodetectors, and a model of the solar    spectrum with no atmosphere.

In accordance with an embodiment of the invention there is provided adevice comprising:

-   a plurality of wavelength filtered photodetectors each receiving    light from the ambient environment within a predetermined wavelength    range and within a predetermined angle of incidence to the normal of    the photodetector;-   a plurality of second photodetectors each receiving light from the    ambient environment;-   a shadow pole disposed with respect to the plurality of second    photodetectors; and-   an optical element disposed on a front face of the device    comprising:    -   a first uniform transparent region disposed in front of the        plurality of second photodetectors and a second diffuser region        comprising a plurality of features, each feature designed in        dependence upon a predetermined wavelength associated with a        wavelength filtered photodetector and the material from which        the optical element is formed.-   a transparent dome that sits above the front surface of the device    and protects the diffuser, shadow pole and second plurality of    photodiodes from the elements.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 depicts a global solar spectral irradiance meter (SolarSIM-G)according to an embodiment of the invention with diffuser attached andremoved;

FIG. 2 depicts exploded assembly views of the SolarSIM-G according to anembodiment of the invention depicted in FIG. 1;

FIG. 3 depicts an exploded cross-sectional assembly view of theSolarSIM-G according to an embodiment of the invention depicted in FIG.1;

FIG. 4 depicts exploded views of the SolarSIM-G housing according to anembodiment of the invention depicted in FIG. 1;

FIG. 5 depicts a plan view and cross-sectional perspective views of adiffuser plate according to an embodiment of the invention as employedwithin the SolarSIM-G according to an embodiment of the inventiondepicted in FIG. 1;

FIG. 6 depicts a perspective view and cross-sectional perspective viewsof a shadow pole and photodetector element according to an embodiment ofthe invention as employed within the SolarSIM-G according to anembodiment of the invention depicted in FIG. 1;

FIG. 7 depicts a perspective view and cross-sectional perspective viewsof a filter and enclosure according to an embodiment of the invention asemployed within the SolarSIM-G according to an embodiment of theinvention depicted in FIG. 1;

FIG. 8A depicts a perspective view and cross-sectional perspective viewsof a tube collimator according to an embodiment of the invention asemployed within the SolarSIM-G according to an embodiment of theinvention depicted in FIG. 1;

FIG. 8B depicts the optical path within an embodiment of the inventionas employed within the SolarSIM-G according to an embodiment of theinvention depicted in FIG. 1;

FIG. 9 depicts an assembly structure and data flow for a SolarSIM-Gaccording to an embodiment of the invention depicted in FIG. 1;

FIG. 10 depicts a processing flow for result generation for a SolarSIM-Gaccording to an embodiment of the invention depicted in FIG. 1;

FIG. 11 depicts a global solar spectral irradiance meter (SolarSIM-G)according to an embodiment of the invention with protective dome andouter mechanical housing attached and removed;

FIG. 12 depicts exploded views of the SolarSIM-G housing according to anembodiment of the invention depicted in FIG. 11;

FIG. 13 depicts an exploded cross-sectional assembly view of theSolarSIM-G according to an embodiment of the invention depicted in FIGS.11 to 12;

FIG. 14 depicts exploded and exploded cross-section assembly views ofthe optical diffuser-filter-optical collimator elements within theSolarSIM-G according to an embodiment of the invention depicted in FIGS.11 to 13;

FIG. 15A depicts a cross-section assembly view of the opticalsub-assembly comprising optical diffuser-filter-optical collimator-andphotodetector elements within the SolarSIM-G according to an embodimentof the invention depicted in FIGS. 11 to 14;

FIG. 15B depicts a single ray tracing within a SolarSIM-G according toan embodiment of the invention depicted in FIGS. 11 to 14;

FIG. 15C depicts a SolarSIM-G according to an embodiment of theinvention.

FIG. 16 depicts an assembly structure and data flow for a SolarSIM-Gaccording to an embodiment of the invention depicted in FIG. 11; and

FIG. 17 depicts a processing flow for result generation for a SolarSIM-Gaccording to an embodiment of the invention depicted in FIG. 11.

DETAILED DESCRIPTION

The present invention is directed to global solar spectral irradianceand more particularly to compact, no-moving part field deployabledevices and methods of measuring and resolving global, direct anddiffuse solar spectral irradiance, together with aerosol, water vapourand ozone spectral absorption profiles.

The ensuing description provides representative embodiment(s) only, andis not intended to limit the scope, applicability or configuration ofthe disclosure. Rather, the ensuing description of the embodiment(s)will provide those skilled in the art with an enabling description forimplementing an embodiment or embodiments of the invention. It beingunderstood that various changes can be made in the function andarrangement of elements without departing from the spirit and scope asset forth in the appended claims. Accordingly, an embodiment is anexample or implementation of the inventions and not the soleimplementation. Various appearances of “one embodiment,” “an embodiment”or “some embodiments” do not necessarily all refer to the sameembodiments. Although various features of the invention may be describedin the context of a single embodiment, the features may also be providedseparately or in any suitable combination. Conversely, although theinvention may be described herein in the context of separate embodimentsfor clarity, the invention can also be implemented in a singleembodiment or any combination of embodiments.

Reference in the specification to “one embodiment”, “an embodiment”,“some embodiments” or “other embodiments” means that a particularfeature, structure, or characteristic described in connection with theembodiments is included in at least one embodiment, but not necessarilyall embodiments, of the inventions. The phraseology and terminologyemployed herein is not to be construed as limiting but is fordescriptive purpose only. It is to be understood that where the claimsor specification refer to “a” or “an” element, such reference is not tobe construed as there being only one of that element. It is to beunderstood that where the specification states that a component feature,structure, or characteristic “may”, “might”, “can” or “could” beincluded, that particular component, feature, structure, orcharacteristic is not required to be included.

Reference to terms such as “left”, “right”, “top”, “bottom”, “front” and“back” are intended for use in respect to the orientation of theparticular feature, structure, or element within the figures depictingembodiments of the invention. It would be evident that such directionalterminology with respect to the actual use of a device has no specificmeaning as the device can be employed in a multiplicity of orientationsby the user or users. Reference to terms “including”, “comprising”,“consisting” and grammatical variants thereof do not preclude theaddition of one or more components, features, steps, integers or groupsthereof and that the terms are not to be construed as specifyingcomponents, features, steps or integers. Likewise, the phrase“consisting essentially of”, and grammatical variants thereof, when usedherein is not to be construed as excluding additional components, steps,features integers or groups thereof but rather that the additionalfeatures, integers, steps, components or groups thereof do notmaterially alter the basic and novel characteristics of the claimedcomposition, device or method. If the specification or claims refer to“an additional” element, that does not preclude there being more thanone of the additional element.

A “portable electronic device” (PED) as used herein and throughout thisdisclosure, refers to a wireless device used for communications andother applications that requires a battery or other independent form ofenergy for power. This includes devices, but is not limited to, such asa cellular telephone, smartphone, personal digital assistant (PDA),portable computer, pager, portable multimedia player, portable gamingconsole, laptop computer, tablet computer, a wearable device and anelectronic reader.

A “fixed electronic device” (FED) as used herein and throughout thisdisclosure, refers to a wireless and/or wired device used forcommunications and other applications that requires connection to afixed interface to obtain power. This includes, but is not limited to, alaptop computer, a personal computer, a computer server, a kiosk, agaming console, a digital set-top box, an analog set-top box, anInternet enabled appliance, an Internet enabled television, and amultimedia player.

A “server” as used herein, and throughout this disclosure, refers to oneor more physical computers co-located and/or geographically distributedrunning one or more services as a host to users of other computers,PEDs, FEDs, etc. to serve the client needs of these other users. Thisincludes, but is not limited to, a database server, file server, mailserver, print server, web server, gaming server, or virtual environmentserver.

An “application” (commonly referred to as an “app”) as used herein mayrefer to, but is not limited to, a “software application”, an element ofa “software suite”, a computer program designed to allow an individualto perform an activity, a computer program designed to allow anelectronic device to perform an activity, and a computer programdesigned to communicate with local and/or remote electronic devices. Anapplication thus differs from an operating system (which runs acomputer), a utility (which performs maintenance or general-purposechores), and programming tool (with which computer programs arecreated). Generally, within the following description with respect toembodiments of the invention an application is generally presented inrespect of software permanently and/or temporarily installed upon a PEDand/or FED.

“Electronic content” (also referred to as “content” or “digitalcontent”) as used herein may refer to, but is not limited to, any typeof content that exists in the form of digital data as stored,transmitted, received and/or converted wherein one or more of thesesteps may be analog although generally these steps will be digital.Forms of digital content include, but are not limited to, informationthat is digitally broadcast, streamed or contained in discrete files.Viewed narrowly, types of digital content include popular media typessuch as MP3, JPG, AVI, TIFF, AAC, TXT, RTF, HTML, XHTML, PDF, XLS, SVG,WMA, MP4, FLV, and PPT, for example, as well as others, see for examplehttp://en.wikipedia.org/wiki/List_of_file_formats. Within a broaderapproach digital content mat include any type of digital information,e.g. digitally updated weather forecast, a GPS map, an eBook, aphotograph, a video, a Vine™, a blog posting, a Facebook™ posting, aTwitter™ tweet, online TV, etc. The digital content may be any digitaldata that is at least one of generated, selected, created, modified, andtransmitted in response to a user request, said request may be a query,a search, a trigger, an alarm, and a message for example.

A “scaffold” or “scaffolds” as used herein, and throughout thisdisclosure, refers to a structure that is used to hold up, interfacewith, or support another material or element(s). This includes, but isnot limited to, such two-dimensional (2D) structures such as substratesand films, three-dimensional (3D) structures such as geometricalobjects, non-geometrical objects, combinations of geometrical andnon-geometrical objects, naturally occurring structural configurations,and manmade structural configurations. A scaffold may be solid, hollow,and porous or a combination thereof. A scaffold may contain recesses,pores, openings, holes, vias, and channels or a combination thereof. Ascaffold may be smooth, textured, have predetermined surface profilesand/or features. A scaffold may be intended to support one or more othermaterials, one or more films, a multilayer film, one type of particle,multiple types of particles etc. A scaffold may include, but not belimited to, a spine of a device and/or a framework, for example, whichalso supports a shell and/or a casing.

A “shell” as used herein, and throughout this disclosure, refers to astructure that is used to contain and/or surround at least partiallyand/or fully a number of elements within a device according toembodiments of the invention. A shell may include, but not limited to, apart or parts that are mounted to a scaffold or scaffolds that supportelements within a device according to an embodiment of the invention.

A “casing” as used herein, and throughout this disclosure, refers to astructure surrounding a scaffold and/or shell. This includes structurestypically formed from an elastomer and/or silicone to provide a desiredcombination of properties to the device it forms part of and otherproperties including, but not limited to, hermeticity, liquid ingressbarrier, solid particulate ingress barrier, surface sheen, physicaltactile surface, and colour. A casing may include, but not limited to, apart or parts that are mounted to a scaffold or scaffolds and/or acasing or casings forming part of a device according to an embodiment ofthe invention.

A “polyester” as used herein, and throughout this disclosure, refers toa category of polymers that contain the ester functional group in theirmain chain. This includes, but is not limited to polyesters which arenaturally occurring chemicals as well as synthetics through step-growthpolymerization, for example. Polyesters may be biodegradable or not.Polyesters may be a thermoplastic or thermoset or resins cured byhardeners. Polyesters may be aliphatic, semi-aromatic or aromatic.Polyesters may include, but not be limited to, those exploitingpolyglycolide, polylactic acid (PLA), polycaprolactone (PCL),polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethyleneadipate (PEA), polybutylene succinate (PBS), polyethylene terephthalate(PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate(PTT), and polyethylene naphthalate (PEN).

A “thermoplastic” or “thermosoftening plastic” as used herein andthroughout this disclosure, refers to a category of polymers that becomepliable or moldable above a specific temperature and solidify uponcooling. Thermoplastics may include, but not be limited, polycarbonate(PC), polyether sulfone (PES), polyether ether ketone (PEEK),polyethylene (PE), polypropylene (PP), poly vinyl chloride (PVC),polytetrafluoroethylene (PTFE), polyimide (PI), polyphenylsulfone(PPSU), polychlorotrifluoroethene (PCTFE or PTFCE), florinated ethylenepropylene (FEP), and perfluoroalkoxy alkane (PFA).

A “metal” as used herein, and throughout this disclosure, refers to amaterial that has good electrical and thermal conductivity. Suchmaterials may be malleable and/or fusible and/or ductile. Metals mayinclude, but not be limited to, aluminum, nickel, copper, cobalt,chromium, silver, gold, platinum, iron, zinc, titanium, and alloysthereof such as bronze, stainless steel, brass, and phosphor bronze.

A “silicone” as used herein, and throughout this disclosure, refers to apolymer that includes any inert, synthetic compound made up of repeatingunits of siloxane.

An “elastomeric” material or “elastomer” as used herein, and throughoutthis disclosure, refers to a material, generally a polymer, withviscoelasticity. Elastomers may include, but not be limited to,unsaturated rubbers such as polyisoprene, butyl rubber, ethylenepropylene rubber, silicone rubber, fluorosilicone rubber,fluoroelastomers, perfluoroelastomers, and thermoplastic elastomers.

A global spectral irradiance meter (SolarSIM-G) is an instrument forresolving the global, direct and diffuse solar spectral irradiancetogether with aerosol, water vapour and ozone spectral absorptionprofiles over a predetermined wavelength range, for example 280nm≤λ≤4000 nm as described below with respect to the embodiment of theinvention depicted in FIGS. 1 to 10. Accordingly, the SolarSIM-Gaccording to embodiments of the invention combines capabilities frommultiple instruments such as a spectroradiometer, pyranometer, sunphotometer, pyheliometer and a weather station all in one single compacthousing. As described below in respect of an embodiment of the inventionin FIGS. 1 to 10 the SolarSIM-G provides six spectral channels althoughit would be evident that more or less spectral channels can be implantedalthough, typically, reductions will result in corresponding performanceand/or feature reduction. Accordingly, a SolarSIM-G according to anembodiment of the invention comprises:

-   -   a plurality of spectral channels in conjunction with custom        shaped mini-diffusers for each spectral channel to optimize its        cosine response;    -   a diffuse light sensor;    -   other ambient environmental sensors as measure inputs; and    -   software algorithm that resolves the global, direct, and diffuse        solar spectra, along with spectral, atmospheric aerosol, water        vapour and ozone transmission profiles.

As will become evident from the description below in respect of FIGS. 1to 9 each spectral channel comprises a photodiode-collimation tube-bandpass filter combination which limits the field of view that eachphotodiode senses from the filter. This eliminates high incident anglelight from hitting the photodiodes which eliminates the centralwavelength shift that the band-pass filters exhibit with high incidentangle light.

As will become evident from the description below in respect of FIGS. 1to 9 the diffuse irradiance sensor consists of a shadow pole surroundedby several small photodiodes that enable the device to estimate theratio of diffuse/global light and estimate the diffuse irradiance. Theknowledge of diffuse to global ratio allows the SolarSIM-G to activelycorrect for the cosine response of the instrument and aids the softwarealgorithm in resolving the global, direct and diffuse solar spectra.

Referring to FIG. 1 there are depicted first and secondthree-dimensional (3D) perspective views 100A and 100B respectively of aSolarSIM-G according to an embodiment of the invention with and withoutthe front diffuser plate attached. In FIG. 2 first and second 3Dperspective views 200A and 200B respectively are depicted of theSolarSIM-G as an exploded assembly. The SolarSIM-G depicted in FIGS. 1to 3 being a 6 channel design operating over a predetermined wavelengthrange, e.g. 280 nm≤λ≤4000 nm. Accordingly, the descriptions in respectof FIGS. 2-9 reflect this 6 channel design but it would be evident toone of skill in the art that alternate embodiments with varying channelcounts may be implemented. Similarly, it would be evident that elementssuch as the diffuse light sensor may be omitted. As depicted theelements include

-   -   Diffuser plate 270;    -   Optical bandpass interference filters 260;    -   Diffuse Light and Temperature Sensor (DILITS) 280;    -   Enclosure 250    -   Collimation tube 230;    -   Main PCB 220;    -   Ambient environment sensor 290;    -   Backplate 210, and    -   Waterproof membrane vent 240.

Now referring to FIG. 4 there are depicted first and second 3Dperspective views 400A and 400B respectively of the SolarSIM-G externalhousing elements which provide the exterior surfaces of the SolarSIM-Gand the barriers to direct ingress etc. both directly and at theirinterfaces. These external housing elements comprising baseplate 210,enclosure 250, and diffuser plate 270. As depicted the enclosure 250forms the majority of the external housing to which the diffuser plate270 mounts on the top and the baseplate 210 to the bottom.

The diffuser plate 270 receives the light from an entire hemisphere andscatters it an all directions (forward and backward). For the opticalwavelength range of 280 nm≤λ≤4000 nm, for this embodiment of theinvention, PTFE or Teflon™ are examples of materials for forming thediffuser. The diffuser plate 270 scatters the light incident on theupper face of the SolarSIM-G and is required to scatter independently ofincident angle such that the light to a photodetector is coupled at allincident angles in order to achieve a good cosine response. Without adiffuser plate 270, at large incident angles the light would be mostlyreflected and would not be detected, and a cosine response is notachieved. The SolarSIM-G diffuser plate 270, as pictured in FIG. 5 infirst to third views 500A to 550C provides a dual functionality. It actsas a front cover for the shadow pole and photodetectors and a diffuserfor the wavelength selective photodetectors at the same time. The sixprotruding areas 520 of the diffuser body 510 are diffusers for eachwavelength filter within the SolarSIM-G. The geometry of these sixmini-diffusers is optimized to achieve the best cosine response for itscorresponding wavelength range of interest. Each filter therefore has aspecific diffuser 520 design in the embodiment depicted. However, inother embodiments of the invention depending upon the design of thediffuser and the optical properties of the different diffuser designsmay be required or in some embodiments may not be required for one, twoor more of the wavelength channels. The window 530 within the diffuserplate 270 is transparent and provides a cover to the shadow pole and itsassociated photodetectors.

Within embodiments of the invention the diffuser plate 270 may be formedfrom an optically transparent material over the wavelength range ofinterest and the protruding areas 520 are made diffusing throughprocessing of the material, e.g. sandblasting, etching etc. leaving thewindow 530 transparent. Alternatively, the body of the diffuser elementmay be formed from a diffusing but optically transparent material overthe wavelength range of interest and the window 530 is formed from aseparate material which is clear and optically transparent material overthe wavelength range of interest.

Within other embodiments of the invention the SolarSIM-G diffuser plate270 may be formed from other materials transparent over the wavelengthrange of interest such as a glass for example. Optionally, theSolarSIM-G diffuser plate 270 may be formed from two or more elementsrather than a single piece or even different diffuser elements perchannel. In other embodiments the diffuser may be transparent and may befrosted and/or translucent.

As depicted in FIGS. 1 to 9 the SolarSIM-G employs six channels withcenter wavelengths (CWLs) at approximately 410-430 nm, 480-505 nm,600-620 nm, 670-690 nm, 860-880 nm, and 930-960 nm. Further, the regionof the diffuser body 510 above the DILITS 280, depicted as area 530, maybe flat, as depicted, or alternatively employ a surface profile. Asevident in second view 500B with cross-section X-X the inner surface ofthe diffuser body 510 there is a recess to align each filter with itsrespective mini-diffuser. Further, as evident in third view 500C withcross-section Y-Y the region of the diffuser body 510 above the DILITS280 is also recessed.

The DILITS 280 within the SolarSIm-Gas depicted in FIGS. 1 to 4 allowsthe G-SolarSIM to determine the ratio of the global incident irradianceversus the diffuse irradiance. As depicted in FIG. 6 with 3D perspectiveview 600A and cross-sectional 3D perspective view 600B this isaccomplished through the use of a shadow pole 750 (protruding metallicpiece) formed within the upper surface of the external enclosuretogether with a recess 730 into which the DILITS 280 sits. The shadowpole 750 projects through an opening 640 within the DILITS 280 and issurrounded by several small photodetectors 630 which are mounted to aPCB 610 which forms the bulk of the DILITS 280. Optionally, the smallphotodetectors 630 may be replaced by one or more detector arrays.Throughout the day, the sun's apparent motion in the sky causes theshadow pole 750 to cast its shadow onto different photodiodes 630. Thisblocks the direct beam of sunlight from those photodiodes 630 that areshadowed, and we can effectively estimate the diffuse irradiance inrelative terms. Optionally, the region of the diffuser body 510 over theDILITS 280 may be transparent rather than diffusing or translucent. Thephotodetectors 630 that are not covered by the shadow report the globalirradiance (diffuse+direct beam irradiance) whilst those that arecovered report the diffuse beam irradiance. The ratio of the twoprovides information about the magnitude of the diffuse irradiance andthe atmospheric conditions. For example, on a very cloudy day, we canexpect the readings from each photodetector to be approximately thesame. On a clear day, the shadowed photodetectors will report lowirradiance, whilst the others will report relatively high irradiance.

The knowledge of the diffuse to direct beam ratio is important forseveral reasons. The active cosine response correction can be performedon the instrument if this ratio is known. Under laboratory conditions,the instruments cosine response is determined by having a nearlycollimated light source shine light onto the instrument at variousangles. The response of the instrument is compared against an idealcosine response and a correction is obtained. However, under outdoorconditions, the instrument does not “know” how much light is comingdirectly at some angles versus the other angles. By establishing thedirect to diffuse ratio we can accurately determine how much light iscoming from the direct beam irradiance as we know the position of thesun at all times throughout the day.

The shadow pole is positioned “behind” the filters to eliminate theshadowing of the filters at low solar elevations angles. Within anembodiment of the invention, the shadow pole is oriented due north,while the arrow like arrangement of the filters points to the south. TheDILITS 280 also includes a temperature sensor 620 for adjusting thetransmission of the diffuser for temperature. It is convenientlypositioned on the diffuse light sensor PCB 610, which is connected tothe main PCB 220.

The enclosure 250 provides the means to hold everything together andprotects components from the weather elements. The enclosure 250 asdepicted in FIGS. 1 to 4 is depicted in 3D perspective view 700A andfirst and second cross-section 3D perspective views 700B and 700Crespectively in FIG. 7. As depicted the upper outer surface comprisesthe recess 730 within which is shadow pole 750 as well as opening 760.Also depicted are the six filter recesses 720 within each of which is anaperture 740. The upper surface also contains an O-ring slot for theinsertion/placement of an O-ring between the enclosure and the diffuserwhich allows the diffuser to seal the enclosure against moisture anddebris ingress. The enclosure also has a cavity for desiccant toregulate the humidity inside the device.

Each of the bandpass interference filters pass a narrow band of light tothe photodiode around their CWL. For the embodiment described in respectof FIGS. 1 to 9 these CWLs are at approximately 410-430 nm, 480-505 nm,600-620 nm, 670-690 nm, 860-880 nm, and 930-960 nm respectively. Thesecan be off-the-shelf hard-coated and rugged filters capable ofwithstanding outdoor environments. Within the embodiment of theinvention described with respect to FIGS. 1 to 9 the filters arecircular and may be discrete or within a housing wherein the geometryand depth of the recesses on the enclosure and diffuser adapt to suit.

Within the enclosure as depicted in FIGS. 2 to 3 sits a collimation tube230 as depicted by 3D perspective view 800A, end-view 800B, and firstand second cross-sections 800C and 800D representing cross-sections X-Xand Y-Y respectively. The function of the collimation tube 230 is tolimit the photodiodes view to light within a specific range of angularincidence. The bandpass interference filters are designed to operate atnormal incidence. The center wavelength blue-shifts (approaches UVspectral range) as the incidence angle increases. However, most bandpassinterference filters exhibit negligible shift up at angles of incidenceof 0°-10°. Therefore, the purpose of the collimation tube is to “filterout” the light for angles greater than near optimal angle of acceptance(which depends on the filter specifications).

The collimation tube 230 is coated to minimize absorption across thewavelengths of interest, namely 280 nm≤λ≤4000 nm. For example, analuminium baffle with black anodizing provides one physical embodiment.Each collimation tube comprises a tube within which are baffles in orderto prevent light reflecting off the walls and onto the detectors. Thewalls may also be threaded or have their surfaces modified to minimizespecular reflections. Since the collimation tube 230 is a separatecomponent to the enclosure, the latter doesn't have to be black anodizedor treated in the same manner to absorb light.

The optical path is shown in FIG. 8B where the incoming light undergoesthe following transformation:

-   -   the diffuser 520 scatters the light in all directions    -   the scattered light passes through the filter 860    -   the filtered scattered light is limited by the front aperture        740;    -   the remaining light that has the right incidence angle passes        through the baffle 850 and hits the active area of the        associated photodiode 870.

The photodetectors 870 are electrically coupled to a main PCB 220 whichis positioned at the bottom of the collimation tube 230 and retainedtogether with the collimation tube 230 by the enclosure 250 and backplate 210. The enclosure 250 and back plate may be similarly designedwith an O-ring seal and screw/bolt mounting as the diffuser plate 270 isattached to the enclosure 250 although other liquid and particlebarriers may be employed within other embodiments of the invention suchas soldering the back plate 210 onto the enclosure 250 or employing agasket between the enclosure 250 and the back plate 210. The main PCB220 provides all of the analog data acquisition and passes thisinformation through a communications protocol to a host. For example, anRS-485 communication protocol may be employed from the SolarSIM-G to ahost computer. However, it would be evident that the SolarSIM-G and hostcomputer may be linked by other wired and wireless protocols includingbut not limited to IEEE 802.11, IEEE 802.15, IEEE 802.16, IEEE 802.20,UMTS, GSM 850, GSM 900, GSM 1800, GSM 1900, GPRS, ITU-R 5.138, ITU-R5.150, ITU-R 5.280, IMT-1000, DSL, Dial-Up, DOCSIS, Ethernet, G.hn,ISDN, MoCA, PON, and Power line communication (PLC). Optionally, thehost computer may be associated with an installation, for example, ofwhich the SolarSIM-G forms part. In other embodiments of the inventionthe host may be remote and, in some instances, may be a remote serverrather than a remote computer.

Also connected to the main PCB 220 are the diffuse light sensor PCB 610and ambient environment PCB 290, the latter of which senses ambienttemperature, pressure and humidity. The later, in order to accomplishthe desired measurement is connected to a waterproof membrane vent 240that allows ambient air to pass through but not water. The ambient PCB220 monitoring the environment is sealed with silicone or O-ring to thewaterproof membrane vent 240 which may also provide for pressureequalization between the inner environment of the SolarSIM-G and ambientexternal environment.

Within embodiments of the invention an outer protective cover, e.g.dome, may be deployed to protect the diffuser element from the ambientenvironment. This outer protective cover being designed such that itallows the sunlight to impinge upon the shadow pole and the plurality ofdetectors around the shadow pole in addition to the collimator tubes forthe wavelength filtered channels. Within embodiments of the inventionwith a dome it would be evident that the diffuser element may bedesigned according to different design guidelines as the diffuserelement is now not providing environmental protection. Accordingly, thewindow (e.g. window 530 in FIG. 5) may be omitted such that no otherelement is disposed between the shadow pole and the dome. In thisinstance the diffuser element (e.g. diffuser element 510) may bedisposed to only cover part of the upper surface of the SolarSIM-G.Optionally, the diffuser structures, e.g. protruding areas 520, may bedisposed only within the collimator tube openings or within and aroundthe collimator tubes.

Optionally, a fan may be disposed to blow periodically and/orcontinuously across the outside of the outer protective cover in orderto mitigate soiling.

Now referring to FIG. 9 there is depicted an exemplary system blockdiagram of a SolarSIM-G according to an embodiment of the invention asdepicted in FIGS. 1 to 8 respectively comprising first to fourthfunctional blocks 900A to 900D respectively. As depicted firstfunctional block 900A relates to the multiple wavelength channels andconsists for each wavelength a mini-diffuser, optical filter, opticalcollimator (tube) collimator, photodiode and multiplexer. The output ofthe multiplexer is coupled to a transimpedance amplifier (TIA) andconverted to digital form via an analog-to-digital converter (ADC). Theoutput of the ADC is coupled to the electronic functional block 900D.Within another embodiment of the invention each photodetector has anassociated TIA and the multiple TIA outputs are multiplexed for the ADCor multiple ADCs.

Second functional block 900B relates to diffuse/direct irradiance andcomprises the diffuser, shadow pole, photodetectors around the shadowpole, wherein the photodetector outputs are multiplexed and coupled tothe TIA and converted to digital form via an analog-to-digital converter(ADC). Optionally, the photodetector outputs are coupled to TIAs andthen multiplexed to one or more ADCs. The output of the ADC is coupledto the electronic functional block 900D. Third functional block 900Crelates to the other sensors including, but not limited to, ambienttemperature, pressure, humidity, diffuser temperature, internaltemperature, and accelerometer. The outputs of these being also coupledto the electronic functional block 900D.

The electronic functional block 900D therefore receives multiplexeddigital data relating to the multiple wavelength channels, multiplexeddata relating the photodiodes around the shadow pole, and digital datafrom multiple environmental sensors. These are processed by amicrocontroller within the electronic functional block 900D via asoftware algorithm or software algorithms stored in memory associatedwith the microcontroller. The electronic functional block 900D alsoimplements one or more communication protocols such that the raw and/orprocessed data are pushed to or pulled to a host computer, in thisinstance a remote server 910 via a network 950. The remote server 910processes the data from the SolarSIM-G or stores processed data from theSolarSIM-G. This data may include, but is not limited to, globalspectral irradiance (horizontal or titled), direct spectrum, diffusespectrum, spectral water vapour, aerosols, and ozone absorptionprofiles.

A software block diagram for the software algorithm of a SolarSIM-G isdepicted in FIG. 10. As indicated all of the inputs on the left are fedto a series of initial processing algorithms and subsequentreconstruction algorithms in order to resolve the global, direct anddiffuse solar spectrum. Accordingly, as indicated the channelresponsivity is derived in dependence upon the internal SolarSIM-Gtemperature, the channel calibration, the nominal channel responsivityand the diffuser temperature. The raw digitized photocurrents andcurrent calibration data are used, with or without the diffuse to globalirradiance ratio to generate (final) calibrated channel data. Thisdiffuse to global irradiance ratio being generated in dependence uponthe shadow pole photodetector currents, their calibration data, andsolar position data derived from a solar position algorithm exploitingdate, time, and location data. This solar position data also defines theair mass zero (AM0) spectrum which is that of the sun with nointervening atmosphere. These outputs are combined with accelerometer,ambient pressure and ambient temperature in an initial algorithm toderive a reconstructed solar spectrum with extracted water vapour,aerosols, and ozone as a result of the wavelengths selected for the sixchannels.

Next the diffuse spectral irradiance is estimated and then employed togenerate a refined reconstructed solar spectrum which is then employedto reconstruct the final global spectrum, diffuse and direct spectra aswell as the atmospheric absorption profiles for water, ozone, andaerosols.

As the global spectrum is a combination of the direct and the diffusespectral irradiances, the first reconstruction will not be perfect, aswe are not taking the diffuse irradiance into account. However, thereconstructed proxy spectrum allows estimating the aerosols, watervapour and ozone content in the atmosphere, which in turn allow a betterapproximation of the diffuse irradiance (which is further enhanced bythe global to diffuse ratio as determined by the shadow polephotodiodes). The approximated diffuse irradiance is then subtractedfrom the proxy global solar spectrum and reconstruction is performedonce again, which gives the direct component of the global spectralirradiance. Addition of the estimated diffuse spectral irradiance to thedirect component yields the global spectral irradiance.

The embodiment of the invention described and depicted in respect ofFIG. 9 exploits six wavelength channels at CWLs of 410-430 nm, 480-505nm, 600-620 nm, 670-690 nm, 860-880 nm, and 930-960 nm. Referring toTable 1 the association of these wavelengths to atmospheric componentsare listed.

TABLE 1 Bandpass Filter CWL Association to Atmospheric ComponentsChannel CWL (nm) Atmospheric Component 410-430 Aerosols 480-505 Aerosols600-620 Ozone 670-690 Aerosols 860-880 Aerosols 820-850, 930-960 Watervapour

For aerosols, other wavelengths may be considered including, forexample, CWLs of 770-790 nm, 1040-1060 nm, 1240-1260 nm, and 1640-160nm. Beneficially, wavelengths below approximately 1100 nm can bedetected with silicon photodetectors whereas longer wavelengths requiregermanium (Ge) or indium gallium arsenide (InGaS) photodetectors.

Now referring to FIG. 11 there are depicted first and secondthree-dimensional (3D) perspective views 1100A and 1110B respectively ofa SolarSIM-G according to an embodiment of the invention with andwithout a protective dome and outer mechanical housing attached.Disposed within the top surface of the SolarSIM-G depicted in first andsecond 3D perspective views 1100A and 1110B respectively are tilt bubble1310 and solar noon indicator 1110. The solar noon indicator 1110 mustbe positioned so that it points toward the solar noon at the location ofthe SolarSIM-G installation, for example due south in the northernhemisphere. It would be evident from FIG. 12 that the optical train fromthe integrating sphere (spherical diffuser) lies along this line suchthat the optical collimators are aligned north-south.

In FIG. 12 first and second 3D perspective views 1200A and 1200Brespectively are depicted of the SolarSIM-G of FIG. 11 as an explodedassembly from two different perspective viewpoints. The SolarSIM-Gdepicted in FIGS. 11 and 12 being a 7 channel design operating over apredetermined wavelength range, e.g. 280 nm≤λ≤4000 nm. Accordingly, thedescriptions in respect of FIGS. 13 to 17 reflect this 7 channel designbut it would be evident to one of skill in the art that alternateembodiments with varying channel counts may be implemented. Accordingly,as depicted within FIG. 12 and first perspective view 1200A the elementsinclude

-   -   Protective dome 1210;    -   Upper diffuser body 1220;    -   Lower diffuser body 1225;    -   Outer mechanical housing 1230;    -   Electrical connector 1235;    -   Electrical circuit board 1240;    -   Ambient environment sensor(s) 1245;    -   Mounting plate 1250;    -   SolarSIM-G base plate 1255;    -   Optical filter assembly 1260;    -   First optical collimator element 1270;    -   Second optical collimator element 1280; and    -   Photodetector circuit board 1290.

FIG. 13 depicts an exploded cross-sectional assembly view of theSolarSIM-G according to an embodiment of the invention depicted in FIGS.11 and 12 where the outer mechanical housing 1230 and protective dome1210 are depicted in correct physical relationship rather than forcompact presentation in FIG. 12. Accordingly, as depicted these elementsare:

-   -   Protective dome 1210;    -   Tilt bubble 1310;    -   Outer mechanical housing 1230;    -   Upper diffuser body 1220;    -   Lower diffuser body 1225;    -   Electrical connector 1235;    -   Electrical circuit board 1240;    -   Gore™ vent 1320;    -   O-ring 1330;    -   SolarSIM-G base plate 1255;    -   Mounting plate 1250;    -   Optical filter assembly 1260;    -   First optical collimator element 1270;    -   Second optical collimator element 1280; and    -   Photodetector circuit board 1290.

FIG. 14 depicts exploded cross-section assembly views of the opticaldiffuser-filter-optical collimator elements within the SolarSIM-Gaccording to an embodiment of the invention depicted in FIG. 11 whereineach optical filter assembly 1260 comprises an optical filter 1260Bwithin a housing 1260A. In contrast FIG. 15A depicts a cross-sectionassembly view of the optical sub-assembly comprising opticaldiffuser-filter-optical collimator-and photodetector elements within theSolarSIM-G according to an embodiment of the invention depicted in FIGS.11 to 14 respectively allowing the optical path from external ambientenvironment to each of the photodetectors 1560 on the photodetectorcircuit board 1290. Also depicted is the internal temperature sensor1590.

Now referring to FIG. 15B a single normal incident axial ray is tracedwithin the optical assembly. Accordingly, light from the ambientenvironment passes through the protective dome 1210 and a portion ofthis light will pass through the precision aperture 1510 formed fromaperture ring 1570 fitted to the upper diffuser body 1220. Accordingly,this light therefore reflects and diffuses within the integrating sphere(spherical diffuser) formed from the mating of upper diffuser body 1220and lower diffuser body 1225 before exiting through outlet aperture 1520formed in the lateral wall of the upper diffuser body 1220 into diffusercavity 1530 formed by the first optical collimator element 1270 and theouter wall of the upper diffuser body 1220.

Disposed within the region around the lower half of the outlet aperture1520 is diffuser baffle 1580 which prevents direct reflective paths fromthe precision aperture 1510 to the outlet aperture. The inner surfacesof the integrating sphere (spherical diffuser) formed by the mating ofupper diffuser body 1220 and lower diffuser body 1225 are within anembodiment of the invention coated with a paint providing broad spectralLambertian-like light diffusion across the wavelength range of interest,e.g. a white paint. Within other embodiments of the invention theseinner surfaces may be roughened via sand blasting, for example, ratherthan as machined.

The light within the diffuser cavity 1530, which may be similarly coatedand treated as the inner surfaces of the integrating sphere (sphericaldiffuser), is then coupled via the optical collimator formed by thefirst and second optical collimator elements 1270 and 1280 respectivelyto each photodetector 1560 and their associated electronics onphotodetector circuit board 1290. Disposed within each opticalcollimator formed by the first and second optical collimator elements1270 and 1280 respectively is an optical filter 1260B within its housing1260A. Within the first and second optical collimator elements 1270 and1280 respectively are first and second collimator apertures 1540 and1550. Accordingly, the overall combination of optical elements providesthe desired cosine response in respect of the performance of theSolarSIM-G.

Now referring to FIG. 15C there is depicted a variant of the SolarSIM-Gdepicted in FIGS. 11 to 15B wherein the precision optical aperture andprotective dome on the top of integrating sphere (spherical diffuser)1220 are replaced with a diffuser element 1500, such as one formed fromPTFE for example. This diffuser element 1500 may provide an improvedcosine response relative to the precision aperture within the thinsheet.

Now referring to FIG. 16 there is depicted an exemplary system blockdiagram of a SolarSIM-G 1600 according to an embodiment of the inventionas depicted in FIGS. 11 to 15 respectively comprising first to thirdfunctional blocks 1600A, 1600B and 900D of the SolarSIM-G 1600. Asdepicted first functional block 1600A relates to the multiple wavelengthchannels and consists of integrating sphere (spherical diffuser) anddiffuser cavity 1530 which are common to all channels and then for eachwavelength an optical filter and optical collimator assembly coupled toa photodiode and then the outputs from the multiple photodetectors arecoupled via an array of transimpedance amplifiers (TIAs) to anelectrical multiplexer. The output of the multiplexer is converted todigital form via an analog-to-digital converter (ADC). The output of theADC is coupled to the electronic functional block 900D. Within anotherembodiment of the invention each photodetector has an associated TIA andthe multiple TIA outputs are multiplexed for the ADC or even multipleADCs may be employed. Optionally, the outputs from the photodetectorsare multiplexed prior to being amplified by a TIA and digitized.

Second functional block 1600C relates to the other sensors within theSolarSIM-G 1600 including, but not limited to, ambient temperature,ambient pressure, ambient humidity, internal temperature, internalhumidity and accelerometer. The outputs of these being also coupled tothe electronic functional block 900D.

The electronic functional block 900D therefore receives multiplexeddigital data relating to the multiple wavelength channels and digitaldata from multiple environmental sensors. These are processed by amicrocontroller within the electronic functional block 900D via asoftware algorithm or software algorithms stored in memory associatedwith the microcontroller. The electronic functional block 900D alsoimplements one or more communication protocols such that the raw and/orprocessed data are pushed to or pulled to a host computer, in thisinstance a remote server 910 via a network 950. The remote server 910processes the data from the SolarSIM-G or stores processed data from theSolarSIM-G. This data may include, but is not limited to, globalspectral irradiance (horizontal or titled), direct spectrum, diffusespectrum, spectral water vapour, aerosols, and ozone absorptionprofiles. Optionally, the data acquired by the SolarSIM-G is processeddirectly onboard the SolarSIM-G prior to be transmitted to the remoteserver 910 or another device via the network 950.

The SolarSIM-G may employ one or more wireless interfaces to communicatewith the network 950 selected from the group comprising, but not limitedto, IEEE 802.11, IEEE 802.15, IEEE 802.16, IEEE 802.20, UMTS, GSM 850,GSM 900, GSM 1800, GSM 1900, GPRS, ITU-R 5.138, ITU-R 5.150, ITU-R5.280, and IMT-1000. Alternatively, the SolarSIM-G may employ one ormore wired interfaces to communicate with the network 950 selected fromthe group comprising, but not limited to, DSL, Dial-Up, DOCSIS,Ethernet, G.hn, ISDN, MoCA, PON, and Power line communication (PLC).

A software block diagram for the software algorithm of a SolarSIM-G isdepicted in FIG. 17. As indicated all of the inputs on the left are fedto a series of initial processing algorithms and subsequentreconstruction algorithms in order to resolve the global, direct anddiffuse solar spectrum. Accordingly, as indicated the channelresponsivity is derived in dependence upon the internal SolarSIM-Gtemperature, the channel responsivity calibration and the channelresponsivity. The raw digitized photocurrents and current calibrationdata are used to generate calibrated channel photocurrents. The date,time, and location information are employed within a solar positionalgorithm which is employed in generating the air mass zero (AM0)spectrum which is that of the sun with no intervening atmosphere. Theseoutputs are combined with accelerometer, ambient pressure and ambienttemperature in an initial algorithm to derive a reconstructed solarspectrum with extracted water vapour, aerosols, and ozone as a result ofthe wavelengths selected for the seven channels of the SolarSIM-G.

Next the diffuse spectral irradiance is estimated and then employed togenerate a refined reconstructed solar spectrum which is then employedto reconstruct the final global spectrum, diffuse and direct spectra aswell as the atmospheric absorption profiles for water, ozone, andaerosols. As the global spectrum is a combination of the direct and thediffuse spectral irradiances, the first reconstruction will not beperfect, as we are not taking the diffuse irradiance into account.However, the reconstructed proxy spectrum allows estimating theaerosols, water vapour and ozone content in the atmosphere, which inturn allow a better approximation of the diffuse irradiance (which isfurther enhanced by the global to diffuse ratio as determined by theshadow pole photodiodes). The approximated diffuse irradiance is thensubtracted from the proxy global solar spectrum and reconstruction isperformed once again, which gives the direct component of the globalspectral irradiance. Addition of the estimated diffuse spectralirradiance to the direct component yields the global spectralirradiance.

The SolarSIM-G depicted in FIGS. 11 to 15A is mounted to a surface viathe mounting plate 1250 which permits rotation of the SolarSIM-G priorto locking it down. The SolarSIM-G itself is mounted via its baseplate1255 to the mounting plate 1250 by 3 screws with springs allowing theSolarSIM-G to be levelled via adjustment of these screws and the tiltbubble 1310. The outer mechanical housing 1230 is attached to thebaseplate 1255 via a series of screws and disposed within the baseplate1255 is a vent 1320 which allows pressure equalization for the outdoorenvironment sensor to measure ambient pressure, temperature andhumidity. Vent 1320 provides for pressure equalization of the internalenvironment of the SolarSIM-G with the ambient environment whilst actingas a barrier to liquids such as water and particulates such as dust.

On the upper side of the SolarSIM-G depicted in FIGS. 11 to 15A theprotective dome 1210 fits within a groove formed in the upper surface ofthe outer mechanical housing 1230 and is adhered in position by amaterial such as a silicone or an epoxy for example. The precisionaperture 1510 is formed by the inner opening within the aperture ring1570 which is formed from a very thin piece of material, e.g. 80 μm highpurity nickel sheet, as this ideally should be zero thickness andperfectly reflective, the former to avoid cosine losses and the latterto aid light diffusion within the integrating sphere (sphericaldiffuser). This aperture ring 1570 is similarly sealed against theprecision aperture 1510 via silicone although a mechanical attachmentmay also be employed.

The upper and lower diffuser bodies 1220 and 1225 form an integratingsphere (spherical diffuser) that creates, ideally, a perfect cosineresponse and the inner surfaces are coated with a highly Lambertianmaterial to provide a Lambertian reflectance which is an “ideal” matteor diffusively reflecting surface with apparent brightness constant withobservation angle. Within the embodiment depicted the upper and lowerdiffuser bodies 1220 and 1225 are joined via screws with a lipped jointbetween although within other embodiments of the invention an O-ring orother seal may be employed as may other means of joining the upper andlower diffuser bodies 1220 and 1225 together. The diffuser is thenmounted to the baseplate 1255 via screws.

Within the upper diffuser body 1220 is the output aperture 1520 whichhas formed around its lower half the diffuser baffle 1580 which is usedto prevent a first reflection from the integrating sphere (sphericaldiffuser) at near normal incidence illumination. The diffuser baffle1580 is spherical to allow for azimuthal symmetry, which improves thecosine response. The output aperture 1520 allows light to enter thediffusing cavity 1530 which allows the rays to undergo multiplereflections for optimal diffusion. This diffusing cavity 1530 beingformed from the upper diffuser body 1220 and first optical collimatorelement 1270.

Within the first optical collimator element 1270 are first collimatorapertures 1540 for each wavelength channel. Mounted to the first opticalcollimator element 1270 is second optical collimator element 1280 whichhas wells machined within to house the optical filters 1260B and theirhousings 1260A. Also formed within second optical collimator element1280 are second collimator apertures 1550 which in conjunction with thefirst collimator apertures 1540 define the angular distribution of lightrays allowed to strike each detector. This being necessary as theperformance of bandpass filters degrades as the incidence angleincreases and accordingly only near collimated light, in reality anapproximately 10-degree half angle, is allowed to pass to thephotodetectors 1560.

Within embodiments of the invention the diffuser may be formed from oneor more thermoplastics, polyesters, and glasses according to thewavelength range, cost, diffuser performance etc. required from thediffuser. For example, the diffuser may be BK7 glass. Optionally, theenclosure, baseplate and tube collimator may be formed from a plastic,thermoplastic, polyester, or a metal or formed from different plastics,thermoplastics, polyesters, or metals. Optionally, in embodiments of theinvention the mechanical structure may be encased partially or fullywithin a casing such as a silicone for example. Optionally, theenclosure and tube collimators may be formed as a single piece-part ortwo or more piece-parts.

Specific details are given in the above description to provide athorough understanding of the embodiments. However, it is understoodthat the embodiments may be practiced without these specific details.For example, circuits may be shown in block diagrams in order not toobscure the embodiments in unnecessary detail. In other instances,well-known circuits, processes, algorithms, structures, and techniquesmay be shown without unnecessary detail in order to avoid obscuring theembodiments.

Implementation of the techniques, blocks, steps and means describedabove may be done in various ways. For example, these techniques,blocks, steps and means may be implemented in hardware, software, or acombination thereof. For a hardware implementation, the processing unitsmay be implemented within one or more application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSPDs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described above and/or a combination thereof.

Also, it is noted that the embodiments may be described as a processwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be rearranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin the figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination corresponds to a return of the functionto the calling function or the main function.

Furthermore, embodiments may be implemented by hardware, software,scripting languages, firmware, middleware, microcode, hardwaredescription languages and/or any combination thereof. When implementedin software, firmware, middleware, scripting language and/or microcode,the program code or code segments to perform the necessary tasks may bestored in a machine readable medium, such as a storage medium. A codesegment or machine-executable instruction may represent a procedure, afunction, a subprogram, a program, a routine, a subroutine, a module, asoftware package, a script, a class, or any combination of instructions,data structures and/or program statements. A code segment may be coupledto another code segment or a hardware circuit by passing and/orreceiving information, data, arguments, parameters and/or memorycontent. Information, arguments, parameters, data, etc. may be passed,forwarded, or transmitted via any suitable means including memorysharing, message passing, token passing, network transmission, etc.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a memory. Memory may be implemented within the processor orexternal to the processor and may vary in implementation where thememory is employed in storing software codes for subsequent execution tothat when the memory is employed in executing the software codes. Asused herein the term “memory” refers to any type of long term, shortterm, volatile, nonvolatile, or other storage medium and is not to belimited to any particular type of memory or number of memories, or typeof media upon which memory is stored.

Moreover, as disclosed herein, the term “storage medium” may representone or more devices for storing data, including read only memory (ROM),random access memory (RAM), magnetic RAM, core memory, magnetic diskstorage mediums, optical storage mediums, flash memory devices and/orother machine readable mediums for storing information. The term“machine-readable medium” includes, but is not limited to portable orfixed storage devices, optical storage devices, wireless channels and/orvarious other mediums capable of storing, containing or carryinginstruction(s) and/or data.

The methodologies described herein are, in one or more embodiments,performable by a machine which includes one or more processors thataccept code segments containing instructions. For any of the methodsdescribed herein, when the instructions are executed by the machine, themachine performs the method. Any machine capable of executing a set ofinstructions (sequential or otherwise) that specify actions to be takenby that machine are included. Thus, a typical machine may be exemplifiedby a typical processing system that includes one or more processors.Each processor may include one or more of a CPU, a graphics-processingunit, and a programmable DSP unit. The processing system further mayinclude a memory subsystem including main RAM and/or a static RAM,and/or ROM. A bus subsystem may be included for communicating betweenthe components. If the processing system requires a display, such adisplay may be included, e.g., a liquid crystal display (LCD). If manualdata entry is required, the processing system also includes an inputdevice such as one or more of an alphanumeric input unit such as akeyboard, a pointing control device such as a mouse, and so forth.

The memory includes machine-readable code segments (e.g. software orsoftware code) including instructions for performing, when executed bythe processing system, one of more of the methods described herein. Thesoftware may reside entirely in the memory, or may also reside,completely or at least partially, within the RAM and/or within theprocessor during execution thereof by the computer system. Thus, thememory and the processor also constitute a system comprisingmachine-readable code.

In alternative embodiments, the machine operates as a standalone deviceor may be connected, e.g., networked to other machines, in a networkeddeployment, the machine may operate in the capacity of a server or aclient machine in server-client network environment, or as a peermachine in a peer-to-peer or distributed network environment. Themachine may be, for example, a computer, a server, a cluster of servers,a cluster of computers, a web appliance, a distributed computingenvironment, a cloud computing environment, or any machine capable ofexecuting a set of instructions (sequential or otherwise) that specifyactions to be taken by that machine. The term “machine” may also betaken to include any collection of machines that individually or jointlyexecute a set (or multiple sets) of instructions to perform any one ormore of the methodologies discussed herein.

The foregoing disclosure of the exemplary embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many variations andmodifications of the embodiments described herein will be apparent toone of ordinary skill in the art in light of the above disclosure. Thescope of the invention is to be defined only by the claims appendedhereto, and by their equivalents.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thespirit and scope of the present invention.

What is claimed is:
 1. A device comprising: a spherical diffusercomprising a spherical cavity within an outer body, the spherical cavitycoated with a first near Lambertian material; a first aperture of afirst predetermined diameter formed in a first predetermined position onthe spherical diffuser; a second aperture of a second predetermineddiameter formed in a second predetermined position on the sphericaldiffuser; a baffle disposed in a predetermined relationship relative tothe first aperture and the second aperture, the baffle having apredetermined thickness, is coated with a second near Lambertianmaterial and is disposed on the inner surface of the spherical diffuserand having a geometry defining a predetermined portion of a sphere; aplurality of optical collimators coupled to the second aperture anddefining a maximum angular acceptance angle for each photodetector of aplurality of photodetectors disposed at the distal end of an opticalcollimator from that coupled to the second aperture; and a plurality ofoptical filters, each filter having a passband of predetermined opticalwavelengths and disposed in combination with an optical collimator ofthe plurality of collimators to filter optical signals exiting thesecond aperture.
 2. The device according to claim 1, wherein thespherical diffuser is attached when deployed to a baseplate mounted to astructure and the spherical diffuser is orientated such that the opticalcollimators are aligned north-south and point towards the solar noon atthe location of the installation.
 3. The device according to claim 1,further comprising a first electronic circuit for digitizing aphotocurrent generated by each photodetector of the plurality ofphotodetectors; and a second electronic circuit for generating areconstructed solar spectrum in dependence upon at least the digitizedphotocurrents of the plurality of photodetectors and model of the solarspectrum with no atmosphere.
 4. The device according to claim 3, whereinthe reconstructed solar spectrum is at least one of a final globalspectrum, a diffuse solar spectrum, and a direct solar spectrum.
 5. Thedevice according to claim 1, further comprising generating an absorptionprofile relating to one of atmospheric precipitable water vapour,atmospheric ozone, and atmospheric aerosols; wherein at least one filterof the plurality of filters has its passband of predetermined opticalwavelengths established in dependence upon the one of precipitable watervapour, ozone, and atmospheric aerosols.
 6. The device according toclaim 1, wherein each collimator comprises a first portion with a firstdiameter and a second portion with a second diameter and the associatedfilter of the plurality of filters is disposed between the first portionand the second portion.
 7. The device according to claim 1, wherein thefirst aperture of a first predetermined diameter is defined by anelement formed within a sheet of predetermined thickness having highreflectivity attached to an opening within the spherical diffuser. 8.The device according to claim 7, wherein the sheet is nickel and thepredetermined thickness is less than 100 μm.
 9. The device according toclaim 1, wherein at least one of: the spherical diffuser is formed fromat least two portions joined together; and the first aperture, secondaperture and baffle are all within a common portion of a plurality ofportions assembled to form the spherical diffuser.
 10. The deviceaccording to claim 1, further comprising a second diffuser disposedbetween the second aperture and the plurality of optical collimators.11. A device comprising: a plurality of first photodetectors, each firstphotodetector receiving a predetermined wavelength range of the ambientoptical environment via an optical path comprising a diffuser element, abandpass filter, and an optical collimator to limit the angle ofincident ambient light to within a predetermined range; a plurality ofsecond photodetectors arranged radially around a post projecting abovethe upper surface of the plurality of second photodetectors; and anelectronic circuit comprising a first portion for digitizing aphotocurrent for each first photodetector of the plurality of firstphotodetectors, a second portion for digitizing a photocurrent for eachsecond photodetector of the plurality of second photodetectors, and athird portion for at least one of generating a reconstructed solarspectrum in dependence upon at least the digitized photocurrents of theplurality of first photodetectors, the digitized photocurrents of theplurality of second photodetectors, and a model of the solar spectrumwith no atmosphere.
 12. The device according to claim 11, wherein thereconstructed solar spectrum is at least one of a final global spectrum,a diffuse solar spectrum, and a direct solar spectrum.
 13. The deviceaccording to claim 11, further comprising generating an atmosphericabsorption profile relating to at least one of precipitable watervapour, ozone, an atmospheric aerosol and atmospheric aerosols.
 14. Thedevice according to claim 11, wherein in deployment the plurality offirst detectors are disposed towards the north and the plurality ofsecond detectors are disposed to the south.
 15. The device according toclaim 11, wherein the diffuser element associated with each firstphotodetector of the plurality of first photodetectors is designed independence upon the predetermined wavelength associated with thecorresponding bandpass filter and the material from which the diffuserelement is formed.
 16. The device according to claim 11, furthercomprising an environmental sensing circuit comprising at least one of ahumidity sensor, a pressure sensor and a temperature sensor disposedwithin the device and coupled to the external environment of the deviceby a vent, the vent allowing passage of air but not water.
 17. Thedevice according to claim 11, wherein the plurality of secondphotodetectors consist of one or more photodiode arrays.
 18. A devicecomprising: a plurality of wavelength filtered photodetectors eachreceiving light from the ambient environment within a predeterminedwavelength range and within a predetermined angle of incidence to thenormal of the photodetector; a plurality of second photodetectors eachreceiving light from the ambient environment; a shadow pole disposedwith respect to the plurality of second photodetectors; and an opticalelement disposed on a front face of the device comprising: a firstuniform transparent region disposed in front of the plurality of secondphotodetectors and a second diffuser region comprising a plurality offeatures, each feature designed in dependence upon a predeterminedwavelength associated with a wavelength filtered photodetector and thematerial from which the optical element is formed; a transparent domethat sits above the front surface of the device and protects thediffuser, shadow pole and second plurality of photodiodes from theelements.
 19. The device according to claim 18, wherein in deploymentthe plurality of first detectors are disposed towards the north and theplurality of second detectors are disposed to the south.
 20. The deviceaccording to claim 18, further comprising an environmental sensingcircuit comprising at least a humidity sensor disposed within the deviceand coupled to the internal environment of the device by a vent, thevent allowing passage of air but not water.
 21. The device according toclaim 18, wherein the plurality of second photodetectors are disposedradially around the shadow pole such that an estimate of the ratio ofreceived diffuse light to received direct light can be obtained from theplurality of photocurrents from the plurality of second photodetectors.22. The device according to claim 18, wherein the reconstructed solarspectrum is at least one of a final global spectrum, a diffuse solarspectrum, and a direct solar spectrum.
 23. The device according to claim18, further comprising generating an atmospheric absorption profilerelating to at least one of precipitable water vapour, ozone, anatmospheric aerosol and atmospheric aerosols.
 24. The device accordingto claim 18, wherein the plurality of second photodetectors are aphotodiode array.
 25. The device according to claim 18, furthercomprising a protective element disposed to protect the diffuser fromthe ambient environment and allow sunlight to impinge directly on theshadow pole and the plurality of second photodetectors.
 26. The deviceaccording to claim 25, further comprising a fan disposed to blow airacross the protective element.